An agricultural row crop planter is a machine built for precisely distributing seed into the ground. The row crop planter generally includes a horizontal toolbar fixed to a hitch assembly for towing behind a tractor or other implement. Row units including seed meters are mounted to the toolbar. In different configurations, seed may be stored at individual hoppers on each row unit, or it may be maintained in a central hopper and delivered to the row units on an as needed basis. The row units include ground-working tools for opening and closing a seed furrow, and a seed metering system for distributing seed to the seed furrow.
In its most basic form, the seed meter includes a housing, a seed disc, and a seed chute. The housing is constructed such that it creates a reservoir to hold a seed pool. The seed disc resides within the housing and rotates about a generally horizontal central axis. As the seed disc rotates, it passes through the seed pool where it picks up individual seeds. The seeds are subsequently dispensed into the seed chute where they drop into the seed furrow.
As the agricultural planter row unit travels across fields with variable soil types, soil moisture, residue levels and topography, it can be difficult to maintain constant seed depth and other parameters due to changing conditions which would ideally require varying the row unit down force pressure. For example, farming with higher residue levels also requires higher row unit down force levels as row cleaners, coulters and other attachments require applied force to keep them in the ground and at consistent depths.
At the same time, in many locations there are immovable rocks or other obstructions at or below the soil surface which require the planter row unit to be able to quickly and freely (without undue increase in the row unit down force) rise up and over the obstruction freely and then quickly move back down, leaving a minimum amount of the row unplanted. All this must be accomplished at continually increasing ground speeds.
Traditionally, springs have been used to urge row units downward. Air bag systems have also been used to overcome some of the drawbacks to mechanical spring systems. Air systems provide a more uniform down force through the vertical range of travel, compared to springs, and are somewhat easier to adjust than springs. However due to the compressibility of air and the relatively large volumes required, changes in air pressure are very cumbersome and not adaptable to very fast change and response to in-cab controls on the go. Air bag systems typically have a very large cross-sectional area in relation to the hose feeding the air spring with pressure, which can provide a large multiplication of force and allow for relatively good isolation of one row unit relative to another. However, air bag systems typically do not allow for rapid change of the force being applied, because of the large volume of the air spring in relation to the cross section of the hose supplying the air. Furthermore, as computers and GPS systems have allowed crop production to be managed in a location-specific way as an implement moves through the field, it has become necessary to achieve more rapid changes in the setting or adjustment of the implement. In the case of a planter row unit, it is also necessary to generate a large amount of force. Each individual planter row unit must be able to react to the soil it encounters independently of the other row units.
Therefore, there is a need in the art for improved apparatuses, systems, and/or methods for providing down force at the row units in a way that provides for a sufficient amount of down force for varying types of row units, while also providing a near instantaneous response to variations in soil conditions, obstructions, and other changes in a field being planted.